The gas turbine power plant, as exemplified in the U.S. Pats. to Jubb et al No. 3,791,137, dated Feb. 12, 1974, and Moskowitz et al, No. 4,164,846 dated Aug. 21, 1979, and the article by V. de Biasi entitled "AEP designing a 60-Mw `PFB` gas turbine plant" which appeared in the March 1977 issue of Gas Turbine World magazine, comprise a fluidized bed reactor or combustor in which compressed air from a gas turbine driven compressor is utilized to suspend particles of coal and sulphur dioxide sorbent and to provide the oxygen for support of the burning of the coal. The gaseous products of combustion are conducted from the combustor, through separators for removal of entrained solids (gas clean-up system), to a gas turbine for driving a load, such as an electrical generator.
In the operation of such gas turbine power plants, a problem encountered is compressor surging and damage resulting therefrom upon load loss when the gas turbine is intentionally or accidentally shutdown. Since the fluidized bed combustor and the separator or combustion product clean-up system provides an extremely large volume of pressurized, high temperature gaseous fluid (as for example, a gas volume of about 55,000 cubic feet at a temperature between 371.degree. C. and about 1051.degree. C.) which cannot be dissipated quickly, there occurs flow of gaseous fluid from the fluidized bed combustor in a direction toward the compressor when the plant is shutdown and the compressor output is diminished or dumped. This backflow of hot gaseous fluid causes a back pressure at the compressor discharge port which surges into the compressor and may cause damage to the compressor. Also, further damage to the compressor and other components may occur because of the hot gases, and particulate solids, such as unburned coal, dolomite and ash, entrained in the gaseous fluid.
It is, therefore, an object of this invention to provide a protective control system for a gas turbine power plant having a pressurized, fluidized bed combustor, which system obviates surging of the compressor and entrained solids carryover into the compressor upon loss of turbine loading.
Another object of the present invention is to provide a protection control system for a gas turbine power plant having a pressurized fluidized bed combustor, which system permits shutdown of the plant, including the fluidized bed combustor, without backflow of gaseous fluid from the fluidized bed combustor to the compressor and the resulting surging and damage to the compressor.